1. Field of the Invention
The present invention relates to an auto-tensioner which holds tension of wrapping connecting members such as endless toothed belt and chain to be the predetermined tension.
2. Description of the Related Art
As the conventional auto-tensioner of this kind, the auto-tensioner described in Japanese Examined Utility Model Publication No. 13647/1991 (Kokoku) has been known. This conventional auto-tensioner comprises: an oil seal provided at the other side of the inside of a cylinder having a closed end at one side; a piston which is slidably connected with one end of a rod which slidably passes through on oil sheet while a little clearance to the inside diameter surface of a cylinder is kept; at the piston and the rod, a passage which communicates with a pressure chamber formed at one side of the the piston and a reservoir chamber formed at the other side of the piston; a check valve provided to open the passage when the pressure of the pressure chamber becomes lower than that of the reservoir chamber; and a spring incorporated to assign the property of projection to the rod at the inside of the reservoir chamber.
The above-mentioned conventional auto-tensioner has the following disadvantages. The reservoir chamber is provided only at the opposite side of the pressure chamber of the piston. Accordingly, if the whole length of the auto-tensioner is reduced by shortening the axial length of the reservoir chamber, the volume of the reservoir chamber is reduced and the sufficient amount of operating oil cannot be reserved. Therefore, operating oil falls short and the air may flow into the pressure chamber so that the function of auto-tensioner may be deteriorated. If the function of auto-tensioner is deteriorated, traps of the belt and irregular sound are generated, and it also leads to reduce the lifetime of the belt.